KR100998521B1 - ?? treated membranes - Google Patents

Abstract

An incoherent UV-treated porous halopolymer membrane is disclosed.

Description

Treated membranes

Mutual Reference to Related Applications

This patent application claims priority to US Provisional Patent Application No. 60 / 394,865, incorporated herein by reference and filed on July 11, 2002.

The present invention relates to microporous fluoropolymer membranes exposed to UV treated membranes, in particular UV non-coherent light radiation.

Certain chemical resistant polymer membranes, such as, for example, fluoropolymer membranes, are used to treat challenging fluids such as corrosive or chemically active liquids. Treatment of such fluids requires membranes that are resistant to chemical degradation.

However, many of these fluids that are aqueous based do not adequately wet the membrane surfaces, which generally have low surface energy. This inadequate wetting results in low fluid permeability and / or high pressure drop across the membrane. This phenomenon is generally explained by the generation of sites that favor nucleation and growth of bubbles. Attempts have been made to improve wetting by providing hydrophilic coatings. However, many of these attempts have been unsatisfactory, for example, in that the permeability of such membranes is still low or very slightly improved.

Moreover, some hazardous liquids include high purity water, ozonated water, organic solvents, and corrosive liquids such as concentrated acids or bases. Some of these liquids additionally include oxidants such as peroxides, for example hydrogen peroxide. Such liquids tend to outgas during processing by the membrane.

As the liquids degass, it is believed that these gases displace the liquid from the membrane pores. This substitution phenomenon is called "dewetting" and leads to a reduction in the effective membrane filtration area, which in turn reduces the overall filtration efficiency. Thus, dewetting may result in reduced permeate treatment and / or increased pressure drop.

There have been proposals to reduce the dewetting problem. For example, treatments were applied to the membranes to rewet the dewet membranes by the use of surfactants or by repeated treatment with low surface tension liquids such as isopropanol. Such approaches are not satisfactory because they involve additional costs and process steps to completely remove the solvent.

Thus, there is a need for a wettable membrane that is resistant to dewetting when exposed to degassing liquids. There is also a need for a membrane that is resistant to degradation by hazardous liquids, thereby minimizing or eliminating the release of extractable materials from the membrane into the treated liquid. There is also a need for chemically resistant membranes with high liquid permeability.

The present invention is provided to remedy at least some of the disadvantages of the prior art. These and other advantages of the invention will be apparent from the following description.

The present invention provides a porous halopolymer membrane, preferably a microporous membrane, which is resistant to dewetting.

According to one embodiment of the present invention, a porous halopolymer membrane, wherein the membrane comprises a first surface and a second surface, the thickness is determined by the first surface and the second surface, the critical through the thickness of the membrane Critical wetting surface tension (CWST) is at least 26 dynes / cm, after two or more cycles, the wet / dewet ratio is at least about 0.7, and at least one surface has at least about 1.2 fluorine / carbon (F A porous halopolymer membrane is provided, having a / C) ratio.

In another embodiment, a porous halopolymer membrane, wherein the membrane comprises a first surface and a second surface, the thickness being defined by the first surface and the second surface, the critical wetting surface tension through the thickness of the membrane A porous halopolymer membrane is provided having a water bubble point of at least 26 dynes / cm and at least about 33 psi and at least one surface having a fluorine / carbon (F / C) ratio of at least about 1.2.

Preferably, the membrane is substantially free of extractables, in particular metal residues.

In a more preferred embodiment, a filter comprising the porous halopolymer membrane is provided.

In the method for producing a porous halopolymer membrane according to an embodiment of the present invention, by exposing the porous halopolymer membrane to incoherent UV irradiation, comprising a first surface and a second surface and on the first surface and the second surface Thickness is determined, the critical wetting surface tension through the thickness of the membrane is at least 26 dynes / cm, has a blister point of at least about 33 psi, and the wet / dewet ratio is at least about 0.7 after two or more cycles. And at least one surface having a fluorine / carbon (F / C) ratio of at least about 1.2.

In another embodiment, contacting a porous halopolymer membrane with a liquid to provide a liquid-treated membrane; And exposing the liquid-treated membrane to non-coherent UV radiation, a method of making a porous halopolymer membrane.

The porous halopolymer membrane according to an embodiment of the present invention comprises a first surface and a second surface, the thickness being determined by the first surface and the second surface, the critical wetting surface tension through the thickness of the membrane (critical wetting) surface tension (CWST) is at least 26 dynes / cm, the wet / dewet ratio is at least about 0.7 after two or more cycles, and the at least one surface has a fluorine / carbon (F / C) ratio of at least about 1.2 .

In another embodiment of the invention, the first and second surfaces comprise a first surface and a second surface, the thickness being defined by the first and second surfaces, wherein at least one of the first and second surfaces is at least about 1.2 fluorine / A porous halopolymer membrane is provided having a carbon (F / C) ratio and having a wet / dewet ratio of at least about 0.7 after two or more cycles and comprising low levels of extractable materials.

The porous halopolymer membrane according to another embodiment of the present invention comprises a first surface and a second surface, the thickness being defined by the first surface and the second surface, at least one surface of at least about 1.2 fluorine / It has a carbon (F / C) ratio, has a blister point of at least about 33 psi and includes low levels of extractables.

In another embodiment of the present invention, the first and second surfaces comprise a first surface and a second surface, the thickness being determined by the first surface and the second surface, the critical wetting surface tension through the thickness of the membrane is at least 26 dynes / cm, A porous halopolymer membrane is provided having a water bubble point of at least about 33 psi and having at least one surface having a fluorine / carbon (F / C) ratio of at least about 1.2.

In yet another embodiment, a first surface and a second surface, the thickness being defined by the first surface and the second surface, each of the surfaces is ungrafted and at least about 1.2 fluorine / Having a carbon (F / C) ratio, a critical wetting surface tension through the membrane thickness of at least 26 dynes / cm, a wet / dewetting ratio of at least about 0.7 after two or more cycles, and a low level of extractable A microporous halopolymer membrane comprising materials is provided.

In preferred embodiments of the invention, the porous halopolymer membrane is a microporous membrane.

In some embodiments, the porous membrane has a critical wet surface tension through the thickness of the membrane of 26 to about 30 dynes / cm. In other embodiments, the membrane has a critical wet surface tension through the thickness of the membrane at least about 40 dynes / cm, or at least about 45 dynes / cm.

Method for producing a porous halopolymer membrane according to an embodiment of the present invention, by exposing the porous halopolymer membrane to incoherent UV radiation, comprising a first surface and a second surface and on the first surface and the second surface Thickness is determined, the critical wetting surface tension through the thickness of the membrane is at least 26 dynes / cm, has a blister point of at least about 33 psi, and the wet / dewet ratio is at least about 0.7 after two or more cycles. And at least one surface having a fluorine / carbon (F / C) ratio of at least about 1.2.

According to another embodiment, contacting a porous halopolymer membrane with a liquid to provide a liquid-treated porous halopolymer membrane; And exposing the liquid-treated membrane to non-coherent UV radiation, a method of making a porous halopolymer membrane is provided.

According to another embodiment, contacting a porous halopolymer membrane with a liquid to provide a liquid-treated membrane; And exposing the liquid-treated membrane to incoherent UV radiation, a method is provided for reducing or eliminating dewetting when the porous halopolymer membrane is in contact with a degassing fluid.

Preferably, the incoherent UV radiation has a wavelength in the range of about 140 to about 350 nm. In other embodiments, the liquid-treated membrane is exposed two or more times to incoherent UV radiation.

The present invention provides porous halopolymer membranes that are resistant to dewetting when the porous halopolymer membranes are in contact with outgassing or degassing fluids, especially high temperature liquids. The membranes are chemically stable and wettable by many fluids. Water wettable membranes can be delivered in dry form. The membranes may have low levels of extractable materials, for example they may also be substantially extractable materials (eg particles of metal, organic and / or inorganic residues, and particles of polymeric material Same resins). The membranes of the present invention do not include wetting agents and / or coatings. The membranes are integral membranes and, unlike composite membranes, the surfaces and the interior are made of substantially the same material, and the surfaces and the interior have many of the same properties. The membranes can be used to treat hazardous fluids such as corrosive or chemically active liquids and can be used when the membranes are exposed to harsh environments such as batteries, filtration devices and the like.

The present invention also includes a step of treating a hydrophobic porous halopolymer membrane with ultraviolet (UV) incoherent or non-coherent light irradiation to obtain a UV treated membrane, the porous halopolymer resistant to dewetting. Provided are methods for making membranes. Non-coherent irradiation means that in a light source that emits light, all emitted photons have random phases as they progress. In contrast, coherent irradiation means that in a light source that emits light, all emitted photons are in phase with each other as they progress. For example, lasers emit coherent radiation.

In one embodiment, the present invention provides a porous halopolymer membrane that is hydrophilic and has a higher permeability than porous hydrophobic halopolymer membranes having substantially the same pore size and thickness, wherein the hydrophilic and hydrophobic membranes are substantially the same. Halopolymers. The hydrophilic membrane preferably has at least two times greater water permeability than that of the hydrophobic membrane, and more preferably has at least ten times greater water permeability than that of the hydrophobic membrane. The hydrophilic surface reduces nucleation and / or growth of microbubbles that result from dewetting.

In another embodiment, the present invention includes a first surface and a second surface, the contacting with a degassing fluid on either the first surface or the second surface, the other of the first surface and the second surface Provided is a porous halopolymer membrane resistant to dewetting when maintained at a pressure lower than the pressure of the surface in contact with the fluid.

The invention also provides a method for treating a fluid, comprising passing the fluid through a membrane made according to the invention.

The membranes of the present invention may be prepared from suitable halopolymers, preferably fluoropolymers. The halopolymers may be homopolymers, copolymers, or combinations thereof. Examples of suitable halopolymers are amorphous polymers comprising fluorine, polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polychlorotrifluoroethylene-co-ethylene (E / CTFE-polymer), polytetrafluoroethylene-co-hexafluoropropylene (FEP), polytetrafluoroethylene-co-perfluoro (alkylvinyl ether) (PFA), polytetrafluoroethylene-co-ethylene (E / TFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), copolymers of vinylidene fluoride, perfluoroethylene-propylene copolymers, and polyvinyl chloride.

Membranes of the invention are typically from about 0.01 micrometer (μm) or more, for example from about 0.02 μm to about 10 μm, preferably from about 0.03 μm to about 0.5 μm, more preferably from about 0.03 μm to about Have a nominal pore size of 0.1 μm.

The membranes of the present invention are resistant to dewetting when contacted with outgassing liquids. Thus, dewetting can be prevented for a long time, for example, typically about 1 hour or more, preferably about 2 hours or more, more preferably about 5 hours to about 10 hours or more. For example, in hot concentrated sulfuric acid containing peroxides, dewetting resistance can be implemented for a period of about 5 hours to about 42 hours, or more. Embodiments of the membranes of the present invention, when contacted at 90 ° C. with a mixture comprising hydrogen peroxide, ammonium hydroxide, and water, are defined as five cycles (the cycles are defined below, each cycle being a period of two hours). Cover), or more resistant to dewetting.

Dewetting resistance can be measured by a suitable method such as the following method. A piece of membrane, for example a 47 mm disc, is presoaked in isopropanol and impregnated in deinonize (DI) water to allow the isopropanol in the membrane to be exchanged for water. The membrane is placed in a glass frit connected to a Buchner funnel, connected to a filtration device, for example a vacuum device. 70 ° C., 100 mL of deionized water is placed on one side of the membrane and a vacuum of about −9 inch (about −229 mm) Hg is applied to the other side of the membrane. Since isopropanol may initially be needed in the process of filling the pores of the membrane with water, the membrane can be operated for a long time without dewetting as well as the need for rewetting with isopropanol.

The membrane is visually identified if there is any dewetting during that time when deionized water flows through the membrane. Record the time it takes for the water to pass through. This is the first filtering (or wetting) cycle. The vacuum is maintained for 2 minutes after the upstream side has been emptied to ensure there is any dewetting of the membrane. Remove the vacuum and place the system at atmospheric pressure. The upstream side is refilled with another 100 mL of deionized water at about 70 ° C. to about 80 ° C., left to flow under vacuum with water applied, and then the flow time is recorded while checking for any dewetting. . This is the second (or dewicking) cycle. Typically, the wetting / dewetting ratio is at least about 0.7 for one wetting / dewetting cycle (ie two cycles). For one wetting / dewetting cycle, in more preferred embodiments, the ratio is at least about 0.8, and in some embodiments, the ratio is at least about 0.9. For at least three cycles (wetting / dewetting / wetting), in even more preferred embodiments, the ratio is at least about 0.8 and in some embodiments at least about 0.9. Embodiments of the membranes of the present invention are resistant to dewetting up to 5 cycles (ie wetting, dewetting, wetting, dewetting, wetting).

Some embodiments of the membrane are liquids having surface tension values of about 54 dynes / cm (0.54 erg / mm ² ) or more, and in some embodiments about 72 dynes / cm (0.72 erg / mm ² ) or more Wetting is possible by Certain other embodiments of the membrane are less than 45 dynes / cm (0.45 erg / mm ² ), for example about 33 dynes / cm (0.33 erg / mm ² ), or 26 dynes / cm (0.26 erg / mm ² ) Wetting is possible by liquids with surface tension values.

Embodiments of the porous halopolymer membrane of the present invention have a substantially uniform critical wet surface tension (CWST; as defined, for example, in US Pat. No. 4,925,572) over the thickness of the membrane. For example, in some embodiments, the membrane is at least about 26 dynes / cm (0.26 erg / mm ² ), typically about 30 dynes / cm, throughout the interior of the membrane, ie from one surface to another surface. (0.30 erg / mm ² ) or greater, in some embodiments, has a CWST of about 40 dynes / cm (0.40 erg / mm ² ). Embodiments in accordance with the present invention span the interior of the membrane at least about 44 dynes / cm (0.44 erg / mm ² ), for example at least about 58 dynes / cm (0.58 erg / mm ² ), or at least 72 dynes / have CWSTs greater than cm (0.72 erg / mm ² ).

In some embodiments, the membrane has a CWST in the range of 26 dynes / cm (0.26 erg / mm ² ) to about 30 dynes / cm (0.30 erg / mm ² ) over the interior of the membrane. Such membranes contain hazardous chemicals and are particularly useful for some filtration devices in which resistance to dewetting is desirable, as well as for various assays where a low fluorescence background is desired.

Uniformity of CWST over the thickness of the membrane can be measured by suitable methods, for example as follows. The membrane is in contact with a liquid having a surface tension of at least 26 dynes / cm (0.26 erg / mm ² ). In the case of membranes having a CWST that is substantially uniform over thickness, the liquid is wetted through the membrane (eg, from one surface, through the inside, through the other surface), and the membrane (Which was initially opaque) becomes transparent. In the case of membranes that do not have a substantially uniform CWST, the liquid can spread on the surface to which the liquid is applied, and does not pass through other surfaces, and at least some of the membrane becomes opaque. Without being bound to any particular theory, the refractive index of the liquid is substantially the same as the refractive index of the polymer used to make the membrane. Thus, membranes with substantially uniform CWSTs will be substantially wetted through them, with little or no air (having a different refractive index than the liquid) in the membrane. Thus, the membranes appear transparent. Membranes that do not have substantially uniform CWSTs have air in some of their pores, and because other refractive indices of air scatter light, portions of the membrane appear opaque.

Porous halopolymers of the present invention, in one embodiment, comprise a first surface and / or a second surface having a fluorine / carbon (F / C) ratio of at least about 1.2, preferably at least about 1.5 or more. For example, the F / C ratio may be in the range of about 1.7 to about 1.8. Preferably, UV treatment (described below) does not remove significant amounts of fluorine atoms from the surface (s) of the membrane.

In some embodiments, the membrane has a first and / or oxygen / carbon (O / C) ratio of about 0.15 or less, preferably in the range of about 0.01 to about 0.1, more preferably in the range of about 0.01 to about 0.05 Or has a second surface.

Some embodiments of the membranes according to the invention have a negative zeta potential, for example a negative zeta potential of at least about −3 mV. In exemplary embodiments, the zeta potential may be in the range of about −3 mV to about −11 mV, at a pH of about 4 to about 9.

In some embodiments, particularly if the porous membrane has a pore size of about 0.1 micron or less, the porous halopolymer membrane of the present invention comprises a UV incoherent light treated porous fluoropolymer membrane, wherein the treated The membrane has a blister point of at least about 30% higher than the blister point of the non-UV light treated porous fluoropolymer membrane, having substantially the same thickness and average pore size, wherein the UV treated membrane and the non UV treated membrane Comprises the same fluoropolymer. Without being limited to any particular theory, the fact that the blister point of membranes prepared according to the present invention increases and wetting improves, at least in part, the walls of the pores are wetted and the bubble formation at the wall surface Reflects the fact that it is substantially reduced. Thus, the pores retain water, impregnated pores and wetted pore walls are resistant to the air passing through them, and the blister point increases.

By way of example, in some embodiments of the porous halopolymer membrane according to the invention, for example, when the treated and untreated membranes have a nominal pore size of about 0.02 microns to about 0.1 microns The membrane has a blister point in the range of about 20 to about 25 psi (about 137.8 kPa to about 172.3 kPa), and the UV incoherent light treated membrane has at least about 33 psi (about 227.5 kPa), or about 120 psi (about 827 kPa) or less, for example, about 35 psi (about 241.2 kPa) to about 50 psi (about 344.5 kPa), preferably about 37 psi (about 255.1 kPa) to about 43 psi (about 296.5 kPa) Have

The porous halopolymer membrane of the present invention comprises macropores (pore diameter or width of 50 nm or more), and micropores (pore diameter or width of 0.5 nm to 2.0 nm) or mesopores Very small pores (sometimes referred to as "voids"), such as (or pore diameter or width from 2 nm to about 50 nm), or substantially no. In some embodiments, the membrane does not comprise or substantially contains both micropores and mesopores. Deficiency or absence of micropores and / or mesopores is believed to contribute to making resistance to desorption by helping to prevent nucleation and / or growth of bubbles.

The size of the pores can be assessed by any suitable method, for example by scanning or transmission electron microscopy, atomic force microscopy, bubble point measurement, mercury intrusion porometry, and / or transmission measurement. Can be evaluated. Micropores can be determined by Brunauer, Emmett, and Teller (BET) analytical methods. In some embodiments, the BET surface area of the micropores is about 0.01 to about 0.9 m ² / g, preferably about 0.1 to about 0.7 m ² / g, more preferably about 0.1 to about 0.5 m ² / g to be. The BET volume of the micropores is about 1 × 10 ⁻⁵ to about 1 × 10 ⁻⁴ mL / g, preferably about 1 × 10 ⁻⁵ to about 5 × 10 ⁻⁵ mL / g. In certain embodiments, for example, the membrane has a BET micropore region of 0.48 m ² / g, a micropore volume of 5.04 × 10 ⁻⁵ mL / g, and a multi-point region of 9.99 ± 0.50 m ² / g area), total pore volume of 0.16 mL / g, and average pore diameter of 651.6 mm 3.

Membranes according to embodiments of the present invention are substantially free of particles or loose fibrils. Moreover, the membranes of the present invention can be made to be substantially free of contaminants, especially extractables, for example metal residues. For example, the membrane or filter may contain less than about 500 ppm of extractables, such as less than about 100 ppm, even less than about 50 ppm of extractables (eg, less than about 15 ppm of extractables). S), for example, less than about 1 ppm of extractables. More preferably, the membrane or filter has less than about 30 ppb metallic extractables, such as less than about 15 ppb metallic extractables (eg, less than about 5 ppb metallic extractables). It may include.

In addition, since the preferred membranes and filters according to the invention can be manufactured to be practically chemically inert, the structural integrity of the membrane and filter can be maintained even in prolonged contact with very strong industrial solvents. And substantially no material leaks from the membrane and filter into the fluid in contact with the membrane and filter. Membranes and filters, preferably chemically inert, in the absence of such extractable material are high purity liquids, in particular high purity hazardous liquids (eg corrosive and / or chemically active liquids). This can be usefully used in devices where required.

Membranes prepared according to the present invention contain low levels of extractable materials. Typically, embodiments of membranes made in accordance with the present invention have extractable material levels comparable to natural, unmodified PTFE membranes. Preferably, commercially available unmodified PTFE membranes and UV treated membranes according to the invention, when treated in the same manner, are diluted, for example with acid washes (eg 5% hydrochloric acid). When extracted once or twice with suitable extracts, such as acid solutions, it comprises substantially the same level of extractables.

The membranes of the invention are substantially free of particles and loose fine fibers, as well as coatings (eg, surfaces are not grafted, eg do not include sulfonated polymer coatings), and metal residues. Since it does not contain water, the membrane does not leak substances into the process fluid (eg filtrate and / or retentate). Thus, for example, the membrane does not send organic carbon and sulfur into the processing fluid. The total organic carbon (TOC) content and / or total mineral content of the extract is low.

UV incoherent light irradiated membranes according to preferred embodiments of the invention essentially maintain their tensile strength during the UV treatment. For example, in one embodiment, the membrane comprises a UV light treated porous fluoropolymer membrane, the UV-treated membrane of a non UV-treated porous fluoropolymer membrane having substantially the same thickness. Tensile strengths ranging from about 80% to about 100%, wherein the UV treated and non UV treated membranes comprise the same fluoropolymer.

In addition, the UV treatment does not significantly affect the retention properties of the membrane.

As used herein, "UV non-coherent light irradiation" includes vacuum UV treatment, high power UV treatment, broadband UV treatment, and black body UV treatment. The UV radiation source can, for example, provide a continuous spectrum of wavelengths, a series of peaks, or a single light emitting line. Typically, UV treatment through a low pressure mercury lamp is less preferred for the present invention.

The present invention comprises a first surface and a second surface, the thickness being defined by the first and second surfaces, the wetting surface tension through the thickness of the membrane is at least 26 dynes / cm, and the cycle Provided is a method of making a porous membrane comprising a porous halopolymer membrane, wherein the wet / dewet ratio after roughing is at least about 0.7 and the at least one surface has a fluorine / carbon (F / C) ratio of at least about 1.2. In one embodiment, the method comprises exposing the microporous halopolymer membrane to UV incoherent light irradiation for a desired time. Typically, the method comprises contacting a porous (preferably microporous) membrane with at least one fluid to fill pores of the membrane with the fluid, and irradiating UV non-coherent light to the fluid-filled porous membrane. Exposing to. The method includes repeatedly exposing the membrane to UV incoherent radiation, and typically re-filling the membrane with a fluid between exposure steps to UV radiation.

The UV non-coherent radiation source is preferably one which has broadband. For example, the broadband may comprise a wavelength distribution within a UV subband of about 100 nm to about 400 nm, for example, a subband of about 150 nm to about 350 nm. On the other hand, the source may be narrower band radiation, for example radiation within a narrower subrange, for example about 100 nm to about 200 nm (Vacuum Ultraviolet), about 200 nm to about 280 nm (UVC), about 280 nm to about 315 nm (UVB), and / or about 315 nm to about 400 nm (UVA). The source may also cause more distinct irradiation wavelengths.

Typically, the intensity (or power density) of the Vacuum Ultraviolet (VUV) source is about 1 minute to about 60 minutes, preferably about 5 minutes to about 20 minutes, more preferably about 1 minute to about 5 minutes. During the total treatment time of, it may be in the range from about 5 mW / cm ² to about 100 mW / cm ² , preferably from about 5 mW / cm ² to about 20 mW / cm ² .

Typically, the intensity (or power density) of the broadband source is about 10 seconds for a total pressure of about 5 seconds to about 300 seconds, preferably about 5 seconds to about 120 seconds, preferably for medium pressure mercury lamps. mW / cm ² to about 1000 mW / cm ² , preferably from about 10 mW / cm ² to about 200 mW / cm ² .

Typically, the intensity (or power density) of the pulsed blackbody radiation source is between about 1 second and about 300 seconds, preferably between about 1 second and about 120 seconds, more preferably between about 1 second and about 60 seconds. , About 53,000 mW / cm ² to about 85,000 mW / cm ² .

The UV incoherent radiation source may emit a continuous radiation stream. Various kinds of suitable UV incoherent light sources are commercially available, for example using electrode-containing bulbs, or those using electrodeless bulbs. Suitable light sources are, for example, Fusion UV Systems, Inc. (Gaithersburg, MD) (eg excimer and mercury lamps), Pulsar Remediation Technologies, Inc. (Roseville, CA), UV Process Supply, Inc. (Chicago, IL), USHIO America, Inc. (Cypress, CA), M.D. Excimer, Inc. (Yokohama Kanagawa, Japan), Resonance Ltd. (Ontario, Canada) and Harada Corporation (Tokyo, Japan).

However, in a preferred embodiment, the irradiation source can deliver irradiation pulses in a short burst. Pulsed radiation sources have sufficient energy and can deliver high density radiation. Most preferably, the radiation source is a pulsed, broadband, blackbody radiation source as described in US Pat. No. 5,789,755. Such pulsed, wideband blackbody irradiation assemblies are commercially available from Pulsar Remediation Technologies, Inc., for example.

The UV treatment described above does not remove significant amounts of fluorine atoms from the surface of the membrane. The membranes produced are stable and the treatment is permanent, for example the effects of the UV incoherent treatment are not washed off even under acidic conditions. For example, UV treated PTFE membranes are stable for 5 hours soaking in cold sulfuric acid (96%), and the membranes are preserved even if their physico-chemical properties are heat treated for 3 days in 170 ° C. air. The UV treated PTFE membrane is also stable when exposed in circulating hot sulfuric acid (96%) hydrogen peroxide (up to 3%) mixture.

One or both surfaces of the membrane can be exposed to UV radiation in accordance with the present invention.

Typically, a membrane exposed to UV radiation is brought into contact with at least one fluid, preferably a liquid (eg to fill the pores of the membrane with a liquid) prior to exposing the membrane to UV radiation. Is placed. If desired, the membrane may remain fully or partially impregnated in the fluid during exposure. On the other hand, for example, the membrane may be removed from the fluid prior to exposure.

Various fluids are suitable for contacting the membrane prior to exposure by UV irradiation. Suitable fluids include water (such as deionized water, and heavy water), alcohols, aromatics, silicone oils, trichloroethylene, carbon tetrachloride, fluorocarbons (eg freons), phenols, organic acids, ethers, Hydrogen peroxide, sodium sulfite, ammonium sulfate (eg, t-butyl ammonium sulfate), ammonium sulfite, sodium aluminate, copper sulfate, boric acid, hydrochloric acid, and nitric acid. Typically, the liquid filling the pores of the membrane while the membrane is exposed to UV radiation absorbs in the generated wavelength range of the UV radiation source.

In some embodiments, the membrane is in contact with a plurality of fluids prior to UV treatment. For example, the membrane can be impregnated in a first fluid, such as an organic solvent (such as methanol, ethanol, acetone, or isopropyl alcohol), preferably the first fluid has a high affinity with water Having a surface tension of about 30 dynes / cm or less, and the membrane may also be impregnated in a second fluid (eg, water) to replace the solvent with water. The membrane may then be impregnated in a third fluid, including, for example, an aqueous solution or a non-aqueous solution, so that the water is replaced with an aqueous compound solution. The membrane impregnated with the third fluid is exposed to UV radiation.

The membranes of the present invention may have any suitable form, for example to provide a filter. Thus, for example, the membrane can be a flat sheet, or corrugated, cylindrical, or tubular.

The invention also provides a device, such as a filter device, comprising at least one membrane as described above. Typical filter devices include a housing, an inlet and at least one outlet defining a fluid flow passage, and a membrane of the invention disposed across or in contact with the fluid flow passage. In some embodiments, the filter device comprises a housing, an inlet, a first outlet, and a second outlet; The inlet and the first outlet define a first fluid flow passage between the inlet and the first outlet, the inlet and the second outlet define a second fluid flow passage between the inlet and the second outlet, The membrane of the present invention is disposed across the first fluid flow passage and tangential to the second fluid flow passage.

In some embodiments, the filter device includes additional elements. For example, in one embodiment, the filter device comprises a filter comprising, consisting of, or consisting essentially of, for example, one embodiment of the membrane according to the invention, and also for example a support And / or at least one additional element, such as a drainage layer and / or a buffer layer. The membrane may for example comprise a composite comprising at least one additional element. Suitable supports, drainage and / or buffer layers include, but are not limited to, at least one mesh and porous fabric or nonwoven sheets. The present invention also provides a method for treating a process fluid, eg, a degassing fluid, comprising contacting the membrane or filter described above with a fluid and separating material (eg, particulates) from the fluid. Provide a method. The method may also include recovering the treated fluid, eg, a particle depleted fluid or a particulate-rich fluid.

The following examples are intended to illustrate the invention in more detail, but should not be construed as limiting the invention in any way. The membranes used in the examples below are expanded polytetrafluoroethylene (PTFE) with a nominal pore size of 0.05 microns. Example 8 also uses an expanded PTFE membrane with a nominal pore size of 0.1 micron, as mentioned.

Example 1

This example describes the preparation of a membrane by pulsed blackbody UV radiation according to one embodiment of the invention.

Sheets of commercially available PTFE membrane (Pall Corporation, East Hills, NY), with CWST of 25 dynes / cm (0.25 erg / mm ² ), were impregnated with isopropyl alcohol (IPA), followed by deionized water (DI) Impregnation was performed to replace IPA with deionized water. The membrane was then impregnated in 0.1 M sodium sulfite (Na ₂ SO ₃ ) to replace deionized water and the pores filled with sodium sulfite. The filled membrane was placed 1 inch (2.54 cm) away from a blackbody UV bulb (Model Rip Tide 8; Pulsar Remediation Technologies, Inc., Roseville, Calif.) In air. The membrane was exposed to pulsed broadband blackbody radiation (power density 1.3 kW) for 20 seconds and removed from the radiation exposure. The membrane was refilled with sodium sulfite and re-exposed to blackbody UV radiation for 20 seconds. Re-filling and re-exposure for 20 seconds were repeated three more times to allow the membrane to be exposed to UV radiation for a total of 100 seconds.

The CWST of the treated membrane was 43 dynes / cm (0.43 erg / mm ² ). The fluorine / carbon (F / C) ratio and the oxygen / carbon (O / C) ratio of the surface were measured by X-ray photoelectron spectroscopy (XPS) analysis, which resulted in 1.6 and 0.05, respectively.

Example 2

This example describes another embodiment of the preparation of a membrane by pulsed blackbody UV radiation according to the present invention.

Sheets of commercially available PTFE membrane (Pall Corporation, East Hills, NY), with CWST of 25 dynes / cm (0.25 erg / mm ² ), were impregnated with isopropyl alcohol (IPA), followed by deionized water (DI) Impregnation was performed to replace IPA with deionized water. The membrane was then impregnated in 0.1 M sodium sulfite (Na ₂ SO ₃ ) to replace deionized water and the pores filled with sodium sulfite. The filled membrane was placed 1 inch (2.54 cm) away from a blackbody UV bulb (Model Rip Tide 8; Pulsar Remediation Technologies, Inc.) in air. The membrane was exposed to pulsed broadband blackbody radiation (power density 1.3 kW) for 20 seconds and removed from the radiation exposure. The membrane was refilled with sodium sulfite and re-exposed to blackbody UV radiation for 20 seconds. Re-filling and re-exposure for 20 seconds were repeated two more times to allow the membrane to be exposed to UV radiation for a total of 80 seconds.

The CWST of the treated membrane was 40 dynes / cm (0.40 erg / mm ² ). The fluorine / carbon (F / C) ratio and the oxygen / carbon (O / C) ratio of the surface were measured by X-ray photoelectron spectroscopy (XPS) analysis, and the results were 1.8 and 0.015, respectively.

Example 3

This example describes the chemical resistance of a membrane according to one embodiment of the invention.

A 90 mm flat sheet of the membrane prepared according to Example 1 was exposed to hot sulfuric acid and hydrogen peroxide as follows.

The sheet was pre-wetted by pumping 3 liters of 100% IPA and then the sheet was allowed to soak in IPA for 30 minutes. The sheet was washed with deionized water for at least 1 hour. The sheets were exchanged with 30%, 60% and 90% cold sulfuric acid. The mixture of sulfuric acid (90%) and hydrogen peroxide (10%) (80:20) was heated to 140 ° C. and the heated mixture was seated (90 mm TEFLON ^™ test jig for 3 hours at an inlet pressure of 30 psi (about 206.7 kPa) In the middle). Acid flow was measured at the beginning and end of the test. The sheet was cooled, exchanged with 60% and 30% sulfuric acid and then with deionized water.

The results are as follows. The CWST before exposure was 43 dynes / cm (0.43 erg / mm ² ) and after exposure was 45 dynes / cm (0.45 erg / mm ² ). Acid flows at the beginning and end of the test were 162 ml / min and 138 ml / min, respectively.

Experiments show that blackbody UV irradiation of sodium sulfite-filled PTFE membranes produces membranes that can withstand the hazards of hot sulfuric acid and hydrogen peroxide mixtures by maintaining CWST and sulfuric acid flow.

Example 4

This example describes the preparation of a membrane by vacuum UV irradiation according to another embodiment of the invention.

A sheet of commercially available PTFE membrane (Pall Corporation) with a CWST of 25 dynes / cm (0.25 erg / mm ² ) was impregnated with isopropyl alcohol (IPA) and then impregnated with deionized water (DI) to give IPA Substituted with deionized water. The membrane was then impregnated in 0.1 M sodium sulfite (Na ₂ SO ₃ ) to replace deionized water and the pores filled with sodium sulfite. The filled membrane was placed 3 mm away from a high power vacuum UV bulb (EOS-X Model 172; Harada Corp., Tokyo, Japan) Pulsar Remediation Technologies, Inc., emitting a wavelength of 172 nm in nitrogen. The membrane was exposed to VUV radiation (power density 6 mW / cm ² ) for 30 minutes and removed from the radiation exposure. The membrane was refilled with sodium sulfite and re-exposed to VUV radiation for 30 minutes.

The CWST of the membrane was 37 dynes / cm (0.37 erg / mm ² ). The fluorine / carbon (F / C) ratio and the oxygen / carbon (O / C) ratio of the surface were measured by X-ray photoelectron spectroscopy (XPS) analysis, and the results were 1.73 and 0.03, respectively.

Example 5

This example describes the preparation of a membrane by broadband UV radiation according to another embodiment of the invention.

A sheet of commercially available PTFE membrane (Pall Corporation) with a CWST of 25 dynes / cm (0.25 erg / mm ² ) was impregnated with isopropyl alcohol (IPA) followed by impregnation with deionized water (DI) to Substituted with deionized water. The membrane was then impregnated in 0.1 M sodium sulfite (Na ₂ SO ₃ ) to replace deionized water and the pores filled with sodium sulfite. The filled membrane was impregnated in sodium sulfite solution and the top surface of the membrane was left 1/8 inch (about 3.2 mm) below the top surface of the solution. 2 inches (approximately 5.1 cm) from a broadband UV bulb (high power medium pressure mercury lamp) (Model no.VPS 1600; Fusion UV Systems, Inc., Gaitherburg, MD) emitting a surface of the solution at a wavelength of 200 to 600 nm. Located. The membrane was irradiated for 2 minutes at a power density of 4.8 kW.

The CWST of the membrane was 42 dynes / cm (0.42 erg / mm ² ). The fluorine / carbon (F / C) ratio and the oxygen / carbon (O / C) ratio of the surface were measured by X-ray photoelectron spectroscopy (XPS) analysis, and the results were 1.75 and 0.05, respectively.

Example 6

This example describes the preparation of a membrane by broadband UV radiation according to another embodiment of the invention.

A sheet of commercially available PTFE membrane (WL Gore and Associates, Inc., Newark, DE), having a CWST of 23.5 dynes / cm (0.235 erg / mm ² ), was impregnated with isopropyl alcohol (IPA) and then desorbed. Impregnated with ionized water (DI) replaced IPA with deionized water. The membrane was then impregnated in 0.1 M sodium sulfite (Na ₂ SO ₃ ) to replace deionized water and the pores filled with sodium sulfite. The filled membrane was impregnated in sodium sulfite solution and the top surface of the membrane was left below the top surface of the solution. The surface of the solution was placed 2 inches (about 5.1 cm) from a broadband UV bulb (high power medium pressure mercury lamp) emitting a wavelength of 200-600 nm (Model no. VPS 1600; Fusion UV Systems). The membrane was irradiated for 2 minutes at a power density of 4.8 kW.

The UV exposed membrane was removed from irradiation exposure and immersed in deionized water for 1 minute. The membrane was again impregnated with sodium sulfite solution while maintaining the membrane top surface below the top surface of the solution. The membrane was irradiated again for 2 minutes at a power density of 4.8 kW. The membrane was impregnated in deionized water, impregnated in sulfurous acid solution and irradiated six more times with UV exposure for a total of 16 minutes.                 

The CWST of the membrane was 72 dynes / cm (0.72 erg / mm ² ).

Example 7

This example compares the blister point of UV treated membranes according to embodiments of the present invention with the blister point of non-UV treated membranes having substantially the same thickness and pore rating. Membranes obtained from Pall Corporation all had a thickness of 75 microns, W.L. The membranes obtained from Gore and Associates were all 25 microns thick. Each of the membranes had a nominal pore rating of 0.05 microns.

The blister point was measured after mounting the membrane disk on a 47 mm jig, pre-soaked with IPA and exchanging IPA with deionized water for 10 minutes. The membrane, moistened with water, was pressurized from upstream to the surface, the pressure was monitored, and the blister point was reached when bubbles were first observed on the downstream surface.

Non-UV treated membranes were commercially available PTFE membranes (Pall Corporation, East Hills, NY, and W.L. Gore and Associates, Inc., Newark, DE). The blister point of Pall Corporation membranes was 15-20 psi, and W.L. The bubble point of Gore and Associates membranes was 20-25 psi.

Four UV treated PTFE membranes were obtained. The first UV treated membrane was prepared as in Example 5 and had a blister point of 80 psi. The second UV treated membrane was prepared as in Example 2 and had a blister point of 75 psi.                 

A third UV treated membrane was prepared as follows. Sheets of a commercially available PTFE membrane (WL Gore and Associates, Inc.) were impregnated with isopropyl alcohol (IPA) and then impregnated with deionized water (DI) to replace IPA with deionized water. The membrane was then impregnated in 0.1 M sodium sulfite (Na ₂ SO ₃ ) to replace deionized water and the pores filled with sodium sulfite. The packed membrane was placed at a distance of 3 mm from a high power vacuum UV bulb (MECL 02V; MD Excimer, Inc., Yokohama, Japan) that emits a wavelength of 172 nm in nitrogen. The membrane was exposed to VUV radiation for 4 minutes (power density 12 mW / cm ² ). The membrane had a blister point of 45 psi.

A fourth UV treated membrane was prepared as follows. Sheets of a commercially available PTFE membrane (WL Gore and Associates, Inc.) were impregnated with isopropyl alcohol (IPA) and then impregnated with deionized water (DI) to replace IPA with deionized water. The membrane was then impregnated in aqueous t-butyl alcohol solution (35%) to replace deionized water and the pores filled with alcohol. The packed membrane was placed at a distance of 3 mm from a high power vacuum UV bulb (MECL 02V; MD Excimer, Inc.) emitting a wavelength of 172 nm in nitrogen. The membrane was exposed to VUV radiation for 10 minutes (power 12 mW / cm ² ). The membrane had a blister point of 60 psi.

This example illustrates that UV treated membranes according to embodiments of the present invention have an increased blister point when compared to non UV treated membranes having the same thickness and pore rating.

Example 8

This example illustrates the difference in comparing critical wet surface tensions (CWSTs) through the thickness of UV treated membranes prepared in accordance with embodiments of the present invention with non UV treated membranes.

Five sets of membranes were tested and the results are shown in the table below. Wetting solution was prepared from water / ethanol mixtures. Each membrane had a thickness of 75 microns.

The first and second set of membranes (indicated by "a" and "b" in the table below) were commercially available membranes (Pall Corporation) and were not UV treated.

A third set of membranes ("c") was made as follows. A commercially available roll membrane (Pall Corporation) was impregnated with isopropyl alcohol (IPA) and then impregnated with deionized water (DI) to replace IPA with deionized water. The membrane was then impregnated in 0.1 M sodium sulfite (Na ₂ SO ₃ ) to replace deionized water and the pores filled with sodium sulfite. The filled membrane was impregnated in sodium sulfite solution and the top surface of the membrane was kept below the top surface of the solution. The surface of the solution was placed at a distance of 3 inches (about 7.6 cm) from a broadband UV bulb (high power medium pressure mercury lamp) (Model no. VPS 1600; Fusion UV systems) emitting at a wavelength of 200-600 nm. The membrane was irradiated (1 ft / min) at a power density of 4.8 kW.

A fourth set of membranes ("d") was made as follows. A commercially available PTFE membrane (Pall Corporation) was impregnated with isopropyl alcohol (IPA) and then impregnated with deionized water (DI) to replace IPA with deionized water. The membrane was then impregnated in 0.1 M sodium sulfite (Na ₂ SO ₃ ) to replace deionized water and the pores filled with sodium sulfite. The packed membrane was placed at a distance of 3 mm from a high power vacuum UV bulb (MECL 02V; MD Excimer, Inc .; power density of 12 mW / cm ² ) emitting a wavelength of 172 nm in nitrogen. The membrane was exposed to VUV radiation for 4 minutes.

A fifth set of membranes ("e") was made as follows. A commercially available PTFE membrane (Pall Corporation) was impregnated with isopropyl alcohol (IPA) and then impregnated with deionized water (DI) to replace IPA with deionized water. The membrane was then impregnated in 0.1 M sodium sulfite (Na ₂ SO ₃ ) to replace deionized water and the pores filled with sodium sulfite. The filled membrane was placed in air at a distance of 1 inch (2.54 cm) from a blackbody UV bulb (Model Rip Tide 8; Pulsar Remediation Technologies, Inc.). The membrane was exposed to pulsed broadband blackbody irradiation (power density 1.3 kW) for 15 seconds.

CWST of fluid
(dynes / cm) (a)
Nominal pore size 0.05 micron (b)
Nominal pore size 0.1 micron (c)
Nominal pore size 0.05 micron (d)
Nominal pore size 0.05 micron (e)
Nominal pore size 0.05 micron 23.5 Yes Yes Yes Yes Yes 25.0 Yes Yes Yes Yes Yes 26.5 No No Yes Yes Yes

Place each set of membranes on a glass plate, and have a surface tension of 23.5 dynes / cm (0.235 erg / mm ² ), 25.0 dynes / cm (0.25 erg / mm ² ), and 26.5 dynes / cm (0.265 erg / mm ² ) Fluids with were placed on the non-glass contacting surface of each membrane.

Membranes prepared according to embodiments of the invention were transparent and each fluid passed through all parts of the glass-contacting surface to the glass plate. Non-UV treated membranes remained white / opaque and fluid with a surface tension of 26.5 dynes / cm (0.265 erg / mm ² ) did not pass evenly through the glass plate. The fluid with surface tension of 23.5 dynes / cm (0.235 erg / mm ² ) and 25.0 dynes / cm (0.25 erg / mm ² ) passed evenly through the non-UV treated membrane.

This example shows that membranes according to embodiments of the invention have substantially the same CWST for 26 dynes / cm (0.26 erg / mm ² ) through the thickness of the membranes.

Example 9

This example describes that membranes according to embodiments of the present invention have substantially the same CWST through the thickness of the membranes.                 

In this example, various 0.05 micron nominal pore size PTFE membranes were mounted on a holder placed in an observation cell and observed using a microscope-charge coupled device (CCD) camera assembly. The membrane was pressurized with water and the water surrounding the membrane was replaced with a gas (nitrogen) -rich water solution. The pressure was reduced to atmospheric pressure to expose the membrane to a supersaturated water-gas solution and to observe the appearance of the membrane (ie, in terms of change in transparency), and bubble formation on the membrane.

The following membranes were tested: two commercially available PTFE membranes from W.L. Gore and Associates, ALC Pall Corporation, and membranes prepared as described in Examples 4 and 5.

The pressure in the observation cell was increased to 1000 psi, allowing the membrane pores to be filled with water. The nitrogen-rich aqueous solution was replaced with water and the pressure was reduced to atmospheric pressure for about 60 seconds. Each membrane was observed for at least 10 minutes after the first bubbles appeared on the surface.

The UV treated membranes prepared according to Examples 4 and 5 were transparent, and the non UV treated membranes, ie commercially available membranes, had opaque portions (eg white). The transparency of the UV treated membranes indicates that they have a substantially uniform CWST through the thickness of the membrane, while the opacity of non-UV treated membranes indicates that the CWST changes through the thickness of the membrane.                 

The water penetration pressure measured for commercially available membranes was higher than the water penetration pressure measured for UV treated membranes. It is believed that the pore walls of commercially available membranes are less wet or less wet than the pores of UV treated membranes and are therefore more resistant to the passage of water through them.

Example 10

This example describes membranes comprising low levels of extractable materials, in accordance with embodiments of the present invention.

UV treated PTFE membranes with a nominal pore size of 0.05 micron and untreated PTFE (control) membranes were purchased. Control membranes are commercially available (Pall Corporation) and UV treated membranes were prepared as in the third set membrane ("c") of Example 7. The UV treated membrane was presoaked with 25% deionized water / 75% IPA, exchanged with deionized water and treated with 0.1 M Na ₂ SO ₃ . The UV treated membranes were framed, air dried and washed for 12 hours in cold deionized water.

The volume of the extract was 500 ml. The membranes were soaked in an orbital shaker for 4 hours in ambient temperature, 5% HCl. The membranes were removed from the HCl solution and the extracts were measured. The membranes were washed in running deionized water for 10 minutes and then soaked in 500 ml of fresh 5% HCl on an orbital shaker for another 4 hours. Extracts were measured.

The levels of the extracts were determined using the HP 4500 Inductively Coupled Plasma-Mass Spectrometer Model No. Measurement was made using IL-ICP-MS-1. ICP-MS standard method (GLSM-67) was used to analyze the extract.

element UV treated first extraction step (ppb) UV treated second extraction step (ppb) Control first extraction step (ppb) Control second extraction step (ppb) Li <DL <DL <DL <DL Na 3.9 0.6 3.7 0.6 Mg 3.1 0.2 0.4 0.2 Al 977.5 8.4 2.1 0.9 K 2.2 0.5 1.4 0.9 Ca 51.1 1.4 26.4 4.6 Cr 1.7 0.2 0.4 0.2 Mn 1.7 <DL <DL <DL Fe 17.9 1.3 0.5 <DL Co 0.2 <DL <DL <DL Ni 2.4 <DL 0.3 <DL Cu 4.4 <DL <DL <DL Ag <DL <DL <DL <DL Sn <DL <DL <DL <DL Pb 0.1 <DL <DL <DL B 0.2 0.2 0.3 0.4 Ti 0.3 <DL <DL 0.3 Zn 94.7 0.6 0.4 5.0 Ba 0.2 <DL 0.1 0.1 Sum 13.4 13.2

The level of extractables was determined using the HP 4500 Inductively Coupled Plasma-Mass Spectrometer Model No. Measurement was made using IL-ICP-MS-1. ICP-MS standard method (GLSM-67) was used to analyze the extract.

After the second HCl extraction, both the control and UV treated PTFE membranes had similar levels of released metal elements.

Example 11                 

This example describes membranes that are resistant to dewicking, in accordance with embodiments of the present invention.

47 mm membrane disks (prepared according to Example 9) were presoaked in IPA and soaked in deionized water to exchange IPA in the membrane with water. The membrane was placed in a glass frit connected to a Bushner funnel connected to a vacuum source. 70 ° C., 100 mL of water was placed on one side of the membrane and a vacuum of about −9 inch (−228.6 mm) of mercury was applied to the other side of the membrane. While deionized water flowed through the membrane, it was visually checked for any desquamation on the membrane. The time taken for the water to flow through was recorded. This was the first filtration (or wetting) cycle. The vacuum was maintained for 2 minutes after the upstream side was empty, and there was any dewetting of the membrane. The vacuum was removed and the system was placed at atmospheric pressure. The upstream side was refilled with another 100 mL of deionized water at about 70 ° C. to about 80 ° C., allowed to flow with water under the applied vacuum, and the flow time was recorded while checking for any dewetting. This was taken as the second (or dewicking) cycle. Five cycles (ie wetting, dewetting, wetting, dewetting, wetting) were tested for the membrane.

The results were as follows:

Flow rate
mL / cm ² / sec Cycle # 1 Cycle # 2 Cycle # 3 Cycle # 4 Cycle # 5 F _i 0.105 0.101 0.095 0.097 0.094 F _f 0.103 0.097 0.094 0.097 0.092 Flow Rate F _f / F _i 0.92 0.96 0.99 1.00 0.98

The results show that the membranes according to embodiments of the present invention have a wetting / dewetting ratio of at least 0.96 for 5 cycles.

Example 12

This example shows that membranes according to embodiments of the present invention have a lower total organic carbon (TOC) content and are rinsed comparable to that of untreated membranes.

47 mm membrane disk (UV treated membrane, prepared as generally described in Example 5 except that the power density is 6 kW) and untreated control membranes (Pall Corporation, East Hills, NY) Was pre-soaked in 60% IPA / 40% deionized water, washed in three containers of deionized water and then tested for effluent resistant rinse up. Eluent resistance values of 17.8 megaohm x cm were selected as "rinse up" values.

The results were as follows.

Sample Time (min) Immunity (Megaohm x cm) TOC (ppb) Flow rate
(ml / min) Control 79 17.8 4.89 221-225 Control 71 17.8 6.25 215-240 UV treatment 49 17.8 2.57 218-227 UV treatment 60 18.3 2.10 240-282

This example shows that membranes according to embodiments of the present invention have a lower total organic carbon (TOC) content and, if not faster, are rinsed, at least as fast, as compared to untreated membranes. .                 

Example 13

This example describes the chemical resistance of a membrane according to an embodiment of the invention.

A 90 mm flat sheet of membrane prepared according to Example 6 was exposed to hot sulfuric acid solution and hydrogen peroxide as follows.

The sheet was pre-wetted by pumping 3 liters of 100% IPA and then the sheet was allowed to soak in IPA for 30 minutes. The sheet was washed with deionized water for at least 1 hour. The sheets were exchanged with 30%, 60% and 90% cold sulfuric acid. The mixture of sulfuric acid (96%) and hydrogen peroxide (3%) (80:20) was heated to 140 ° C. and the heated mixture was seated (90 mm TEFLON ^™ test jig for 3 hours at an inlet pressure of 30 psi (about 206.7 kPa) In the middle). Acid flow was measured at the beginning and end of the test. The sheet was cooled, exchanged with 60% and 30% sulfuric acid and then with deionized water.

The results are as follows. The CWST before exposure was 72 dynes / cm (0.72 erg / mm ² ) and after exposure was 72 dynes / cm (0.72 erg / mm ² ). Acid flows at the beginning and end of the test were 432 ml / min and 420 ml / min, respectively. The water flow before acid exposure was 1,500 ml / min and the water flow after exposure was 1480 ml / min.

Experiments show that blackbody UV irradiation of sodium sulfite-filled PTFE membranes produces membranes that can withstand the hazards of hot sulfuric acid and hydrogen peroxide mixtures by maintaining CWST, sulfuric acid flow, and water flow.

Example 14

The membrane was prepared as described generally in Example 6 except that a roll of membrane was treated instead of the sheet. The take-up roll and mandrel were rotated at 1,600 rpm and the membrane submerged in 0.1 M sodium sulfite was exposed to broadband UV. The membrane was exposed to UV light for a total of about 15-20 minutes. The membrane had a CWST of 72 dynes / cm (0.72 erg / mm ² ).

A 47 mm flat sheet of dry UV treated membrane was obtained from the roll, which was placed on a vacuum draw down flask. 5 mL of 98% sulfuric acid was poured into the flask and the acid solution was withdrawn through the membrane under a negative pressure of 15 inches of mercury.

After 20 seconds, sulfuric acid drops were collected downstream. The flow rate, 20 drops / second, did not change during that time.

This example shows that the membrane according to an embodiment of the present invention can be fully wetted with ambient sulfuric acid by applying a slight pressure drop.

All references, including publications, patent applications, and patents, cited herein, are incorporated by reference to the same extent, as each reference is individually and specifically pointed out to be incorporated by reference, It is presented here in its entirety.                 

Unless otherwise indicated herein or otherwise clearly indicated by the context, each element in the context describing the invention (particularly within the context of the appended claims) is to be interpreted as including both the singular and the plural. Should be. Citations to ranges of values are only intended to serve as a simple way to independently refer to each individual number within the range, unless otherwise indicated, each individual number being independent of it. Are incorporated into the specification as cited. All methods described herein may be performed in any suitable order unless otherwise indicated herein or explicitly contradicted by context. Any, also all examples, or exemplary language (e.g., "such as") provided herein are intended to better illustrate the present invention and do not limit the scope of the invention unless otherwise claimed. . No term in the specification should be construed as indicating any non-claimed element, as is essential to the practice of the invention.

Preferred embodiments of the invention are described herein, including those known to the inventors in an optimal mode for carrying out the invention. Naturally, variations on such preferred embodiments will be apparent to those skilled in the art upon reading the above description. The inventors expect it to be appropriate for those skilled in the art to employ such variations, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, the present invention includes all modifications and equivalents to the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations is included by the present invention, unless otherwise indicated herein or explicitly contradicted by context.

Claims (41)

A microporous halopolymer membrane, wherein the membrane comprises a first surface and a second surface and is defined by the first and second surfaces, the critical wetting surface tension through the thickness of the membrane. , CWST) is between 40 dynes / cm (0.40 erg / mm ² ) to 72 dynes / cm (0.72 erg / mm ² ), the wetting / dewetting ratio is at least 0.7, and at least of the first surface and the second surface A microporous halopolymer membrane, wherein one surface has a fluorine / carbon (F / C) ratio of at least 1.2. A microporous halopolymer membrane, the membrane comprising a first surface and a second surface, the thickness being defined by the first surface and the second surface, wherein at least one surface of the first surface and the second surface is A microporous halopolymer membrane having a fluorine / carbon (F / C) ratio of at least 1.2 and wherein the membrane has a wetting / desorption ratio of at least 0.7 and comprises less than 100 ppb of extractable material when extracted with 5% hydrochloric acid. . The method of claim 2, A microporous halopolymer membrane, characterized in that the critical wetting surface tension through the thickness of the membrane is 26 dynes / cm (0.26 erg / mm ² ) to 72 dynes / cm (0.72 erg / mm ² ). The method of claim 3, The microporous halopolymer membrane, characterized in that the critical wetting surface tension through the thickness of the membrane is 40 dynes / cm (0.40 erg / mm ² ) to 72 dynes / cm (0.72 erg / mm ² ). A porous halopolymer membrane, the membrane comprising a first surface and a second surface, the thickness being defined by the first and second surfaces, the critical wetting surface tension through the thickness of the membrane is 40 dynes / cm ( 0.40 erg / mm ² ) to 72 dynes / cm (0.72 erg / mm ² ) with a wetting / dewetting ratio of at least 0.7. The method of claim 1, Halopolymer membrane, characterized in that it has a nominal pore size in the range of 0.02 to 0.1 micron. The method according to any one of claims 1 to 6, Halopolymer membrane, characterized in that the critical wetting surface tension through the thickness of the membrane is 45 dynes / cm (0.45 erg / mm ² ) to 72 dynes / cm (0.72 erg / mm ² ). The method of claim 7, wherein Halopolymer membrane, characterized in that it has a critical wet surface tension through the thickness of the membrane of 58 dynes / cm (0.58 erg / mm ² ) to 72 dynes / cm (0.72 erg / mm ² ). The method of claim 7, wherein Halopolymer membrane, characterized in that the halopolymer comprises a fluoropolymer. 10. The method of claim 9, Halopolymer membrane, characterized in that the fluoropolymer comprises PTFE. The method of claim 10, A halopolymer membrane characterized by being resistant to dewetting when contacted with hot water as a degassing fluid. The method of claim 10, At least one surface of the first surface and the second surface has an oxygen / carbon (O / C) ratio of 0.15 or less. delete By exposing the porous halopolymer membrane to incoherent UV radiation, a thickness is defined by the first and second surfaces, the thickness being determined by the first and second surfaces, and the critical wetting surface tension through the thickness of the membrane 26 dynes / cm (0.26 erg / mm ² ) to 72 dynes / cm (0.72 erg / mm ² ), the wetting / dewetting ratio is at least 0.7, and at least one surface of the first surface and the second surface is A method of making a porous halopolymer membrane, having a fluorine / carbon (F / C) ratio of at least 1.2. Contacting the porous halopolymer membrane with a liquid to provide a liquid-treated membrane; And Exposing the liquid-treated membrane to incoherent UV radiation. The method of claim 15, And said liquid-treated membrane is exposed to incoherent UV radiation at least twice. The method according to claim 15 or 16, Contacting the porous halopolymer membrane with a liquid comprises contacting the membrane with first and second, optionally with a third liquid. The method according to claim 15 or 16, Contacting the porous halopolymer membrane with a liquid comprises impregnating the membrane in the liquid; Also Exposing the liquid-treated membrane to incoherent UV radiation comprising exposing the membrane to radiation with the membrane impregnated in the liquid. The method according to any one of claims 14 to 16, The non-coherent UV radiation is characterized in that the black body radiation. The method according to any one of claims 14 to 16, And wherein said non-coherent UV radiation is high power radiation. The method according to any one of claims 14 to 16, Wherein said non-intrusive UV radiation is vacuum UV radiation. The method according to any one of claims 14 to 16, Wherein said halopolymer membrane comprises a fluoropolymer. The method of claim 22, Wherein said fluoropolymer comprises PTFE. A porous halopolymer membrane, which is prepared by exposing the porous halopolymer membrane to incoherent UV radiation according to claim 20. Microporous PTFE membrane, The membrane comprises a first surface and a second surface, the thickness being defined by the first and second surfaces, the microporous PTFE membrane is applied to the microporous PTFE membrane with the pores of the membrane impregnated with liquid. The membrane is modified by irradiating incoherent broadband UV, and the membrane has a thickness of the microporous PTFE membrane and a CWST through the bulk of 26 dynes / cm (0.26 erg / mm ² ) to 72 dynes / cm ( 0.72 erg / mm ² ), the wet / dewet ratio is at least 0.7, the microporous PTFE membrane is free of coating, and the first and second surfaces each have a fluorine / carbon (F / C) ratio of at least 1.2 and A microporous PTFE membrane having an oxygen / carbon (O / C) ratio of 0.01 to 0.15. The method of claim 25, The thickness of the membrane and CWST through the body of the microporous PTFE membrane, characterized in that 30 dynes / cm (0.30 erg / mm ² ) to 72 dynes / cm (0.72 erg / mm ² ). 27. The microporous PTFE membrane of claim 25, wherein the first surface and the second surface each have an F / C ratio of at least 1.5. 28. The microporous PTFE membrane of any one of claims 25 to 27 wherein the zeta potential is in the range of -3 mV to -11 mV at a pH of 4-9. The microporous halopolymer membrane of claim 1 wherein said membrane comprises a PTFE membrane having said F and C ratios of at least 1.5 on said first and second surfaces, respectively. 30. The membrane of claim 1 or 29, wherein the zeta potential is in the range of -3 mV to -11 mV at a pH of 4-9. A fluid filtration method comprising passing a fluid through a microporous membrane according to any one of claims 1, 2 or 25, and obtaining a filtered fluid through the microporous membrane. 32. The method of claim 31, wherein the fluid comprises a corrosive fluid, and the method further comprises obtaining the corrosive fluid filtered through the microporous membrane. 33. The method of claim 32, wherein the corrosive fluid comprises a concentrated acid. 33. The method of claim 32, wherein the corrosive fluid comprises a concentrated base. 33. The method of claim 32, wherein the corrosive fluid comprises an oxidant. 33. The method of claim 32, wherein the corrosive fluid comprises hot concentrated acid. 37. The method of claim 36, wherein the hot concentrated acid comprises sulfuric acid. 38. The method of claim 37, wherein the corrosive fluid further comprises an oxidant. 34. The method of claim 33, wherein the concentrated acid comprises sulfuric acid. 33. The method of claim 32, wherein the corrosive fluid comprises a cold concentrated acid. 41. The method of claim 40, wherein the cold concentrated acid comprises sulfuric acid.